pj84,
That example is built so that any subpanel VIs are expected to be in the same VI library ([labview]\examples\general\controls\subpanel.llb) as the main viewer.vi.
You could do this:
1. Make a copy of that VI library, so that you don't wipe out the shipping example
2. Save your subpanel VIs into your copy of the subpanel.llb library
3. Change the string array on the block diagram of viewer.vi so that it has the names of your subpanel VIs instead of the shipping example VIs
4. Change the ring on the front panel so that it has appropriate names for your VIs
That would work, although it would leave you with a library that has various unnecessary VIs in it. Also, it probably won't teach you much about LabVIEW. You didn't explain what aspect of the example you weren't understanding, so it's hard to give advice, but I would suggest that you read the LabVIEW manuals/help topics on VI Server, subpanels, and ring controls, and then return with any questions you have.
Regards,
John